We all know dolphins are intelligent animals. So intelligent, in fact, that a document called the Declaration of Rights for Cetaceans — which argues that dolphins should be afforded similar rights as humans — has actually been gaining some serious traction among scientists and ethicists in recent years.

Cetaceans, including dophins and whales, are known to play, to communicate using sound, to form…
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One of the most human-like dolphin behaviors is that of the signature whistle. Each dolphin has a unique whistle that, in many ways, is a lot like its name. And while we've known about these whistles for decades, little is known about their use by dolphins in the wild. Now, a team of Scottish scientists has brought us one step closer to making sense of these enigmatic noises.

The research was conducted by researchers Vincent Janik and Nicola Quick of the University of St. Andrews. Janik has been studying dolphins off the coast of Scotland for close to twenty years, but only recently has he learned to accurately monitor the whistles of free-swimming dolphins. After learning the technique while working with researchers in Florida, Janik and Quick returned to Scotland to try it out, where they made a number of unprecedented observations.

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For starters, they learned that when two pods of dolphins encounter one another and merge, 90% of these meetings will be accompanied by signature whistles from members of the uniting pods. The researchers determined that these dolphins do not mimic one another's whistles when meeting up (something we know them to be capable of), but instead stick to their unique, personal call. In other words, it appears as if the dolphins are using the calls to announce their identity to the other group, not to acknowledge the identity of another group's dolphin.

This was not entirely unexpected. It's long been hypothesized that dolphins use signature whistles to identify themselves, and Janik and Quick's findings suggest that, even in the wild, these whistles are used as a sort of greeting ritual. But their recordings also revealed something they had not anticipated: when two dolphin groups merged, it was rare for more than one member of each group to issue its signature whistle. Discover's Ed Yong runs us through four possible explanations for this strange observation:

First, it's possible that the spokes-dolphin is the leader of the group. However, these animals don't live in a particularly hierarchical society, and there's no good evidence for the existence of dolphin leaders. Second, dolphins might not be very choosy about who they associate with, so they don't need to know who they're hanging out with. Again, this seems unlikely, since we know that bottlenose dolphins do have preferred companions. Third, the dolphins might already know who's part of which group, so they only need to hear an individual signature to remember all the others.

But according to Yong, Janik is partial to door number four: "it's very specific animals that are interested in joining up... Just like in a group of people, not everyone wants to join up with others."

Read more — including some great interview transcripts from Vincent Janik and dolphin expert Justin Greggs — over on Not Exactly Rocket Science.